The present invention relates to diffusers for hydro-power plants and more particularly to a submersible diffuser and to a hydro-power or hydroenergy producing plant adapted to receive it.
Diffusers for hydro-energy producing plants such as hydroelectric or hydro pumped-storage plants are, obviously, well known in the art.
THE AIM OF SUCH DIFFUSERS, POSITIONED AT THE WATER OUTLET OF THE TURBINES, IS TO CONVERT THE INHERENT ENERGY DUE TO THE SPEED OF THE WATER INTO ENERGY DUE TO PRESSURE THEREOF. These diffusers are particularly important in low-head hydrogeneration plants.
It is known that in a rectilinear frusto conical diffuser, the highest efficiency is attained when the angle at the vertex of the cone is 6.degree.. If this angle is decreased, friction between the water flowing through the diffuser and the inner surface thereof increases, thus reducing the efficiency of the diffuser.
Similarly, if this angle is increased, then losses are caused due to turbulence and back flow of the water.
It is also known, that the ideal ratio between the diameter of the inlet end of the diffuser and the length thereof, should not be less than 1/10. For water heads of 10 m., this ideal ratio must be around 1/15 for best efficiency.
These parameters, which only take into account hydraulic efficiency considerations, have never been put into practice because a diffuser built with such dimensions would be non economical. Consequently smaller, less efficient diffusers are generally used, although they are still large and costly structures, particularly when they have been designed to be reasonably efficient.
It is an aim of the present invention to enable the construction of optimum diffusers by providing means for manipulating, positioning and mounting such diffusers, with relative ease, in spite of their bulky sizes.
An additional aim of the present invention has been to provide a novel diffuser whereby it is possible to increase the efficiency of a known hydroelectric power plant by easily improving the known diffuser, by one according to the present invention.
This increased efficiency is not a direct consequence of the novel structure of the diffuser, but such novel structure now makes it possible to use a diffuser designed to provide optimum efficiency, and which so far was not manufactured because of its bulky size and expensive construction costs.
An even further aim of the present invention has been to provide a novel structure whereby hydrostructures built for other purposes, such as: flood control systems, navigation development, irrigation intakes, abandoned dikes etc.; can be easily converted into power generating plants.
A further aim of the present invention has been to provide a new method of positioning a diffuser in an energy generating plant such a hydraulic power plant.
According to one aspect of the present invention there is provided a submersible diffuser for an energy producing plant having means for directing water through an energy generating unit for causing actuation thereof, the diffuser comprising a hollow body defined by a lateral or peripheral wall and having a first open end adapted to be positioned against the outlet of said water directing means for receiving the water emerging therefrom, and a second open end for discharging the water entering the first end; the opening of said first end being of smaller cross sectional area than the opening of said second end; at least one chamber defined in said wall and of a volume at least sufficient to cause sinking or floatation of said diffuser when the former is filled with water or gas, respectively; and means for filling the chamber with water for sinking purposes and with gas for floatation purposes.
According to another aspect of the present invention a hydroelectric power plant having means for directing water through a power generating unit for causing actuation thereof, is improved by incorporating therein a diffuser having a hollow body defined by a lateral wall, and having a first open end positioned against the outlet of said water directing means for receiving the water emerging therefrom, and a second open end for discharging the water entering the first end; the opening of said first end being of smaller cross sectional area than the opening of said second end; at least one chamber defined in said wall and having a volume at least sufficient to cause sinking or floating of said diffuser when the former is filled with water or gas respectively; means for filling the chamber with water for sinking purposes and with gas for floatation purposes; and means for movably supporting said diffuser downstream of said power plant and permitting the diffuser to be moved towards and away from said power plant during mounting or dismounting of said diffuser in said power plant.
According to an even further aspect of the present invention, a method is provided for submerging and positioning a diffuser in a hydraulic power plant having means for directing water through a power generating unit for causing actuation thereof, and supporting means extending downstream of said first mentioned means, the method comprising the steps of: a) Taking a diffuser incorporating a hollow body defined by a lateral wall and having a first open end and a second open end; the opening of said first end being of smaller cross sectional area than the opening of said second end; at least one chamber defined in said wall; and roller means, external to said body and secured to each side thereof; b) Floating the diffuser slightly downstream of said power generating unit and oriented so that the longitudinal axis of said body which extends though said ends, is parallel to the axis of said water directing means of the power plant and positioned substantially thereabove; c) Introducing a liquid into said chamber to cause sinking of said diffuser; d) Directing the sinking diffuser so that said roller means rest on said supporting means; e) Drawing the diffuser along the supporting means to position its first open end against the outlet of said water directing means, and; f) Securing the diffuser in such position.
Although reference in the specification is to a rectilinear frusto-conical diffuser, it will be obvious to those skilled in the art, that the teachings of this invention are independent of the specific shape of the diffuser and that such teachings are also applicable to diffusers of any other shape, such as pyramidal and independently of their rectilinear or elbow shaped configuration.